I have a serious problem with Xorg server on ubuntu 12.04 (with nvidia 420M GT card).

At home I am using an external monitor connected to my laptop's HDMI port - the external display is used as extended. But then when I leave my house and go e.g. to work I don't use it anymore but my xorg's config file remains as it was and then some bad things happen. For instance - every time when I boot after disconnecting the external monitor I get some not default font and bigger than usual + some windows with errors about not compatible resolution modes.

But today I have tried to boot normally without the additional monitor and xorg server has failed and I cannot boot to GUI. I am receiving this

I've experienced very much alike phenomenon, spent several hours to figure out. By remove + install xserver-xorg I managed to fix it. I didn't find monitors.xml but only monitors.xml.bk under ~/.config/, just to share. Thanks!!
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IsaacSJan 18 '13 at 7:20

1

After upgrading to 12.10 i had a blank login screen. Turns out xserver-xorg-core was not installed, found that thanks to your answer :-)
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pushyApr 5 '13 at 18:50

I see a very similar issue but apt-get remove xserver-xorg followed by an apt-get install xserver-xorg didn't fix the issue for me... :(
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cerrDec 6 '14 at 17:56